Prahlad, K. V.
M.S. (Master of Science)
Department of Biological Sciences
Estrogen--Physiological effect; Uterus
The effect of varying the time of estrogen injection (during a 24 hour period) on various uterine responses to the hormone was investigated. Adult Sprague-Dawley rats were used throughout these experiments. The parameters measured were uterine wet weight increase, RNA, DNA, protein, and binding of radioactive estrogen. A rhythmic diurnal variation in estrogen-induced biosynthetic response of the uterus was detected. Ovariectomized animals receiving estrogen in the early morning responded significantly more than those given the hormone in the evening. This diurnal variation in uterine response to estrogen was clearest in terms of RNA and wet weight increase and less marked with regard to protein synthesis. The ability of the uterus in ovariectomized rats to bind estradiol-17B seems to vary diurnally. Binding was greater 1 hour after estrogen injection in the evening than 1 hour after morning injections. To investigate any role the adrenal gland might have in maintaining this diurnal variation in uterine response, adreno-ovariectomized animals were given estrogen during the morning and evening. The diurnal variation in estrogen-induced uterine wet weight increase was not present in adreno-ovariectomized animals. Also estrogen was unable to elevate the total uterine protein in these animals. Diurnal variations in uterine RNA synthesis remain unaltered in adreno-ovariectomizedanimals. The role of Triiodothyronine (T₃) during estradiol-17[sub β] action on the uterus of ovariectomized adult rats was also investigated. The effect of T₃ alone and in combination with estradiol-17[sub β] on uterine weight, RNA, ribonucleotide pools, and DNA were observed. The uterine weight of animals receiving T₃ only was increased significantly over that of control rats. Conversely, priming ovariectomized rats with T₃ had little effect on the estrogen induced uterine weight increase; however, the amounts of RNA and ribonucleotide pools were depressed by this treatment. The significant diurnal differences in uterine response to estrogen demonstrate the importance of uniform injection times in other experiments. Although the adrenal seems to play some role in regulating at least a part of the diurnal variation in uterine response to estrogen, the nature of this regulation remains obscure. T₃ priming may have depressed the estrogen-induced uterine RNA and ribonucleotide pools by partially blocking uterine uptake of estrogen. Although T₃ alone increases uterine wet weight, the mechanisms of this action are unknown.
Carlson, Richard A., "Influence of diurnal rhythms and triiodothyronine on the response of the rat uterus to estradiol-17[sub β]" (1971). Graduate Research Theses & Dissertations. 3565.
viii, 92 pages
Northern Illinois University
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